Modern integrated circuits contain many high frequency, high accuracy analog elements such as phase lock loops, LVDS, DDR PHY/IO, etc. It can be difficult to accurately measure such signals during testing and characterization of new integrated circuits, or chips. This can make debugging of circuits difficult and requires the use of expensive test equipment, along with expenditure of significant resources and time.
In some cases test equipment operating externally to the integrated circuit requires complicated synchronization to enable reading of the signals to be tested within a very small measurement window. This is complicated the difficulty in allowing internal signals of the integrated circuit to be read externally to the chip, for example to allow triggering of a measurement based on a different signal. Thus, it is necessary to trigger measurements based on some external timing which may not be accurately synchronized to the event that it is desired to measure.
Furthermore, while the value of a signal at a specified point in time can be measured by the test equipment, it is not possible to measure a time when a switching event occurs. Rather, multiple measurements must be taken, and the data searched for the desired event. Due to the time delays and latencies involved with the use of external test equipment, this makes it difficult to determine an exact time the event occurs, particularly in a modern circuit which may be operating an GHz frequencies.
Due to the above difficulties, characterization and testing of integrated circuit designs can currently require many man months of time to be spent by specialist engineers, which is expensive and may still not result in a fully accurate characterization of the circuit being tested.